Infradian Rhythmicity in Sleep/Wake Ratio in Developing Infants

Although there are several reports on ultradian and circadian rhythms in newborns, we found only one report in which infradian periodicities are described for heart-rate measurements in the early stages of human development. Here, we report infradian rhythms in the monthly range in the sleep/wake cycle of four infants studied along 24 consecutive weeks. Our procedure was applied to sleep diary records from four healthy newborns. The data were arranged in binary time series representing sleep (?1) or wake (1) states. These time series were integrated in order to obtain the cumulative sleep/wake time. A measure of the sleep/wake ratio (SWR) was obtained by computing the average slope of the cumulative sleep/wake time. To extract periodicities we applied the Fourier periodogram to the temporal course of the SWR. We found a notorious difference in the SWR pattern among infants. In two infants the SWR showed a marked linear decay, spending more time asleep than awake, while in the two other infants oscillated near zero. We found robust oscillations in all children. In all cases the Fourier periodogram results present significant power in the infradian range. From these results, we suggest that sleep and wake durations are probably modulated by some internal stimuli.     

An active balance board system with real-time control of stiffness and time-delay to assess mechanisms of postural stability

Increased time-delay in the neuromuscular system caused by neurological disorders, concussions, or advancing age is an important factor contributing to balance loss (Chagdes et al., 2013, 2016a,b). We present the design and fabrication of an active balance board system that allows for a systematic study of stiffness and time-delay induced instabilities in standing posture. Although current commercial balance boards allow for variable stiffness, they do not allow for manipulation of time-delay. Having two controllable parameters can more accurately determine the cause of balance deficiencies, and allows us to induce instabilities even in healthy populations. An inverted pendulum model of human posture on such an active balance board predicts that reduced board rotational stiffness destabilizes upright posture through board tipping, and limit cycle oscillations about the upright position emerge as feedback time-delay is increased. We validate these two mechanisms of instability on the designed balance board, showing that rotational stiffness and board time-delay induced the predicted postural instabilities in healthy, young adults. Although current commercial balance boards utilize control of rotational stiffness, real-time control of both stiffness and time-delay on an active balance board is a novel and innovative manipulation to reveal balance deficiencies and potentially improve individualized balance training by targeting multiple dimensions contributing to standing balance.     

Early changes in mitochondrial monoamine oxidase activity of rat liver during 2-acetylaminofluorene feeding

The activities of mitochondrial type A and B monoamine oxidase were determined in the liver of rats fed a diet containing 2-acetylaminofluorene (AAF). Three days after the initiation of AAF-feeding, there was a significant decrease of type B monoamine oxidase activity without affect on type A enzyme. The decreased activity of type B monoamine oxidase, which reached a minimum after three weeks, was sustained for as long as AAF-feeding was continued. Sex-related difference in response to AAF was seen in the rat with respect to the onset and the intensity of the decreased type B monoamine oxidase activity, male rats being more sensitive to the carcinogen than female rats. In contrast to the in vivo effect, AAF showed a potent inhibitory effect on type A monoamine oxidase, rather than on type B enzyme, when added in vitro. The pI₅₀ values were estimated to be 7.5 against type A monoamine oxidase and 4.1 against type B enzyme, respectively. The in vitro inhibition of both types of monoamine oxidase by AAF was competitive. The K_i values for AAF were calculated to be 9.51 · 10^?9 M for type A monoamine oxidase and 1.30 · 10^?5 M for type B enzyme, respectively. In accordance with the potent inhibitory effect of AAF on type A monoamine oxidase in vitro, a single administration of the carcinogen, at a dose of 50 mg/kg, resulted in a marked and temporal decrease of the enzyme activity in the mitochondria of male rat liver. Recovery of the decreased type B monoamine oxidase activity was slow, and the enzyme activity did not return to control levels, even if rats were fed the basal diet for 2 or 4 weeks after the cessation of AAF-feeding.     

Collagen biosynthesis by human skin fibroblasts III. The effects of ascorbic acid on procollagen production and prolyl hydroxylase activity

Human skin fibroblasts were cultured under conditions optimized for collagen synthesis, and the effects of ascorbic acid on procollagen production, proline hydroxylation and the activity of prolyl hydroxylase were examined in cultures. The results indicated that addition of ascorbic acid to confluent monolayer cultures of adult human skin fibroblasts markedly increased tha amount of [³H]hydroxyproline syntehsized. Ascorbic acid, however, did not increase the synthesis of ³H-labeled collagenous polypeptides assayed independently of hydroxylation of proline residues, nor did it affect the amount of prolyl hydroxylase detectable by an in vitro enzyme assay. Also long-term cultures of the cells or initiation of fibroblast cultures in the presence of ascorbic acid did not lead to an apparent selection of a cell population which might be abnormally responsive to ascorbic acid. Thus, ascorbic acid appears to have one primary action on the synthesis of procollagen by cultured human skin fibroblasts: it is necessary for synthesis of hydroxyproline, and consequently for proper triple helix formation and selection of procollagen.     

Feeding preference by the male blowfly Phormia regina for some natural foods and its relation to carbohydrate, amino acid, and alcohol content

The male blowfly, Phormia regina Meigen shows preference among a variety of natural and artificial foods. In a laboratory study preference was observed among sweet and fermenting juices as well as between liver and fish. The preferences between fresh and fermenting juices were based not only on component sugars, but also on other components, namely, amino acids, alcohol salts and presumably other chemical compounds. The preference between decaying liver and fish was probably based partly on the composition and concentration of amino acids in these foods. A variety of amino acids were found in foods and some of these amino acids were shown to be excitatory, some inhibitory and others neutral. Salts were also observed to be present in the juices; and in a laboratory study NaCl at lower concentrations acted synergestically with 0.1 M sucrose and at higher concentrations repulsive. It is suggested that feeding preference is based on several chemicals which behave either in an excitatory, additive, neutral, inhibitory or synergistic manner. The ratio of excitants to inhibitants is important in deciding the direction of preference.

---

Résumé P. regina Meigen mâle préfere certains aliments naturels ou artificiels. Au laboratoire ses préférences parmi les jus sucrés sont les suivantes: orange > miel > pomme > sucrose 0.1 M; et parmi les aliments en décomposition: sucrose 0.1 M > foie > poisson. Les jus frais sont préférés aux jus fermentés. Les préférences ne dépendent pas seulement de la nature des sucres, mais aussi des acides aminés, de l'alcool, des sels et probablement d'autres substances chimiques. Le foie contient à la fois le plus grand nombre et la concentration la plus élevée en acides aminés, ce qui explique partiellement le goût pour le foie. Expérimentalement on peut classer les acides aminés en stimulants, inhibiteurs et neutres. Des sels ont été notés dans les jus, mais aucune analyse qualitative et quantitative n'en a été faite. Mélangé à du sucrose à 0.1 M, NaCl agit en synergie aux faibles concentrations, devient neutre à 0.175 M et à des concentrations supérieures le sucrose seul est préféré au mélange avec NaCl. Cependant, un mélange de NaCl à 0.25 M (bien qu'une telle concentration soit peu probable dans des jus végétaux) avec du sucrose à 0.1 M était préféré à l'eau. Il en est déduit que les préférences alimentaires. dans la nature sont orientées par plusieurs substances chimiques qui se comportent d'une façon stimulante, additive, neutre, inhibitrice ou synergique, et que les préférences alimentaires sont relatives. Le rapport de stimulants sur inhibiteurs est important dans la détermination du sens de la préférence.

     

Study on the enzymatic 5′-deiodination of 3′,5′-diiodothyronine using a radioimmunoassay for 3′-iodothyronine

A radioimmunoassay for 3′-iodothyronine has been developed. All iodothyronine analogues (except 3,3′-diiodothyronine) showed very little (0.02% at most) cross-reactivity, and the assay was sensitive to 1 pg 3′-iodothyronine/ tube. We have studied the 5′-deiodination of 3′,5′-diiodothyronine by rat liver microsomal fraction in the presence of dithiothreitol. Production of 3′-iodothyronine at 37°C was found to be linear with time of incubation up to 30 min and with concentration of microsomal protein up to 100 μg/ml. The reaction rate reached a limit on increasing 3′,5′-diiodothyronine concentration to 10 μM. The effect of pH on 3′-iodothyronine production was found to depend on 3′,5′-diiodothyronine concentration. Increasing 3′,5′-diiodothyronine concentration from 0.1 to 10 μM resulted in a shift of the pH optimum from 6–6.5 to 7.5. Similar effects on the 5′-deiodination of 3,3′,5′-triiodothyronine were observed, supporting the hypothesis that these reactions are catalysed by a single enzyme (iodothyronine 5′-deiodinase).     

Electron-microscopic and immunocytochemical analyses of Weibel-Palade bodies in the human umbilical vein during pregnancy

Summary The present study was done to elucidate the biological significance of the Weibel-Palade body of human umbilical vein endothelial cells. Quantitative determinations of these endothelial-specific granules throughout pregnancy revealed that their numbers and size per cell profile were maintained at low levels from 12 to 19 weeks of gestation; then both rapidly increased from 33 weeks to full term. This increase coincided with the development of the rough endoplasmic reticulum and an increase in the number of endothelial cell pinocytotic vesicles. Light-microscopic peroxidase anti-peroxidase and electron-microscopic protein A-gold techniques provided evidence that factor VIII-related antigen was localized in the Weibel-Palade bodies. Furthermore, in vitro treatment of incubated umbilical vein tissue with compound 48/80, a histamine releaser, induced degranulation of Weibel-Palade bodies from the endothelium. The present study indicates that Weibel-Palade bodies are storage sites of both histamine and factor VIII-related antigen and have an important role in the obliteration of this vessel.     

Arginase,an s-phase enzyme in a human cell line

Suspension cultures of ‘Chang liver’ cells were synchronized by preincubation in a glutamine-deficient medium or by thymidine blockade. Specific arginase activity varied in the synchronized cultures, being high when the number of S-phase cells was maximal. A relationship between high arginase activity and a high percentage of (S+G₂) cells was also found when unsynchronized cells were separated by velocity sedimentation. The increase in arginase activity near the G₁/S border was totally inhibited in the presence of cycloheximide. The rate of decrease in activity after addition of the drug indicated that the variations in the rate of synthesis of the enzyme, while the rate of degradation was more or less constant, corresponding to 4–6% per h. The role of arginase in cells lacking a urea cycle and the regulation of arginase activity in ‘Chang liver’ cells is discussed.